(1) Field of the Invention
The present invention pertains to the construction of an electromagnetic device, such as an electric motor or electric generator, where component parts of the electromagnetic device have been redesigned to significantly reduce its size.
(2) Description of the Related Art
Current trends in the design of electromagnetic machines such as motors have lead to compact designs of high efficiency motors. The motor designs have obtained high power to weight and high power to size ratios through their use of high magnetic flux density magnets on their rotors and high density windings on their stators.
Compact high efficiency motors are constructed of basically the same component parts of larger motors, those being a casing or housing shell containing the stator, a pair of end shields attached to opposite ends of the stator, and a rotor supported for rotation in the stator bore by a pair of bearings mounted in the end shields.
In the reduction in size of these high efficiency motors the surface areas of motor component parts available for use in establishing secure connections between the component parts is also reduced. For example, in the construction of a larger motor there are typically substantial areas on interfacing surfaces of motor component parts, such as a stator and an end shield, to accommodate connectors such as nut and bolt connectors to securely hold the two component parts together. With the ample areas available on the interfacing surfaces of the component parts, larger connectors may be employed to securely hold the component parts together. However, when the motor is significantly reduced in size, all of its component parts are reduced including the interfacing surfaces of mating component parts and the connectors employed in securely holding the component parts together. In reduced size motors, the component parts must be redesigned in order to provide the needed secure connections between the component parts.
A reduction in motor size also requires positioning all of the motor component parts closer together. This includes the electrical component parts of the motor such as the stator winding, and the structural component parts of the motor such as the end shields. Reduced motor size brings the end shields much closer to the end turns of the stator winding presenting the undesirable possibility of arcing or shorting of the stator winding with the metal end shields. The reduction in size bringing component parts closer together also presents the problem of heat generated in one area of the motor adversely affecting another area of the motor, for example, the electronics of the motor. The component parts of the reduced size motor must be redesigned to avoid the potential problems of shorting and heat affecting motor performance.